Multimedia broadcast multicast service (MBMS) utilizing spatial multiplexing

ABSTRACT

Systems and methods are disclosed herein for an enhanced Multimedia Broadcast Multicast Service (MBMS) in a wireless communications network. In one embodiment, a number of base stations in a MBMS zone, or broadcast region, accommodate both Spatial Multiplexing (SM) enabled user elements and non-SM enabled user elements. In another embodiment, a number of base stations form a MBMS zone, or broadcast region, where the MBMS zone is sub-divided into an SM zone and a non-SM zone. In another embodiment, the wireless communications network includes multiple MBMS zones. For each MBMS zone, base stations serving the MBMS zone transmit an MBMS zone identifier (ID) for the MBMS zone. The MBMS zone ID may be used by a user element for decoding and/or to determine when to perform a handoff from one MBMS zone to another.

This application claims the benefit of U.S. provisional patentapplication Ser. No. 61/038,506, filed Mar. 21, 2008, the disclosure ofwhich is hereby incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to a Multimedia Broadcast MulticastService (MBMS) in a wireless communications network.

BACKGROUND

In Fourth Generation (4G) wireless communications networks such as LongTerm Evolution (LTE) networks, base stations may utilize spatialmultiplexing to increase data rates. Specifically, spatial multiplexingis a transmit scheme that allows a base station having multiple transmitantennas to simultaneously transmit independent and separately encodeddata streams from each of the transmit antennas using the same transmitresources. For instance, using spatial multiplexing, a base station thatutilizes Orthogonal Frequency Division Multiplexing (OFDM) is enabled totransmit independent and separately encoded data streams from each ofmultiple transmit antennas using the same sub-carriers in the same OFDMsymbol periods.

Multimedia Broadcast Multicast Service (MBMS) is a broadcasting servicethat can be offered via existing wireless, or cellular, communicationsnetworks such as Global System for Mobile communications (GSM) networksand Universal Mobile Telecommunications Service (UMTS) networks.However, several issues arise when attempting to implement MBMS in a 4Gwireless communications network where base stations utilize a spatialmultiplexing transmit scheme. Specifically, it is desirable to providethe MBMS service to both spatial multiplexing (SM) enabled user elementsand non-SM enabled user elements. Another issue is that, especially forlarge cells, spatial multiplexing may not be able to be supportedthroughout the entire cell. As such, there is a need for a system andmethod for providing MBMS in a wireless network utilizing spatialmultiplexing.

SUMMARY OF THE DETAILED DESCRIPTION

Systems and methods are disclosed herein for an enhanced MultimediaBroadcast Multicast Service (MBMS) in a wireless communications network.In one embodiment, a number of base stations in a MBMS zone, orbroadcast region, accommodate both Spatial Multiplexing (SM) enableduser elements and non-SM enabled user elements. More specifically,resources within a downlink channel utilized by the base stations in theMBMS zone are partitioned into first resources allocated to a SM modeand second resources allocated to a non-SM mode. The resources of thedownlink channel may be partitioned using a Time Division Multiplexing(TDM) scheme, a Frequency Division Multiplexing (FDM) scheme, or ahybrid TDM and FDM scheme. The base stations simultaneously broadcastmultimedia content for a basic service to both SM enabled user elementsand non-SM enabled user elements within the MBMS zone via the firstresources of the downlink channel allocated for the non-SM mode using anon-SM transmit scheme. The base stations also simultaneously broadcastmultimedia content for an enhanced service to SM enabled user elementswithin the MBMS zone via the second resources of the downlink channelallocated for the SM mode using a SM transmit scheme. By simultaneouslybroadcasting the multimedia content using the same resources of thedownlink channel, the base stations for the MBMS zone form a SingleFrequency Network (SFN) that substantially improves a Signal toInterference plus Noise Ratio (SINR) for user elements located near celledges.

In another embodiment, a number of base stations form a MBMS zone, orbroadcast region, where the MBMS zone is sub-divided into an SM zone anda non-SM zone. Base stations in both the SM zone and the non-SM zonesimultaneously broadcast multimedia content for a basic service to SMenabled user elements within the SM zone. Base stations serving the SMzone simultaneously broadcast multimedia content for an enhancedservice, in addition to the multimedia content for the basic service, toSM enabled user elements within the SM zone using an SM transmit scheme.SM enabled user elements within the SM zone operate in an SM receptionmode while SM enabled user elements within the non-SM zone operate in anon-SM reception mode. Further, when moving from the SM zone to thenon-SM zone, a SM enabled user element may switch from SM reception modeto non-SM reception mode. Likewise, when moving from the non-SM zone tothe SM zone, a SM enabled user element may switch from non-SM receptionmode to SM reception mode.

In another embodiment, the wireless communications network includesmultiple MBMS zones. For each MBMS zone, base stations serving the MBMSzone transmit an MBMS zone identifier (ID) for the MBMS zone. A userelement within an MBMS zone receives the MBMS zone ID for the MBMS zone.The MBMS zone ID may be used by the user element to decode informationreceived from the base stations serving the MBMS zone such as, forexample, signaling information. In addition or alternatively, MBMS zoneIDs may be utilized by a user element to determine when a handoff fromone MBMS zone to another MBMS zone is to be performed.

Those skilled in the art will appreciate the scope of the presentinvention and realize additional aspects thereof after reading thefollowing detailed description in association with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of thisspecification illustrate several aspects of the invention, and togetherwith the description serve to explain the principles of the invention.

FIG. 1 illustrates a Multimedia Broadcast Multicast Service (MBMS) zonein a wireless communications network that accommodates both SpatialMultiplexing (SM) enabled user elements and non-SM enabled user elementsaccording to one embodiment of this disclosure;

FIGS. 2A-2C illustrate a number of exemplary schemes for partitioningresources of a downlink channel utilized to broadcast multimedia contentfor the MBMS zone for both SM enabled user elements and non-SM enableduser elements;

FIG. 3 illustrates a MBMS zone that includes a SM zone and a non-SM zoneaccording to one embodiment of this disclosure;

FIG. 4 is a flow chart illustrating a process by which a SM enabled userelement located within the MBMS zone of FIG. 3 is enabled to select areception mode based on whether the SM enabled user element is locatedin the SM zone or the non-SM zone according to one embodiment of thisdisclosure;

FIG. 5 illustrates a handoff of a user element from the SM zone to thenon-SM zone of FIG. 3 using the process of FIG. 4 according to oneembodiment of this disclosure;

FIG. 6 illustrates multiple MBMS zones within a wireless communicationsnetwork according to one embodiment of this disclosure;

FIG. 7 illustrates a handoff process for a user element that moves fromone MBMS zone to another MBMS zone according to one embodiment of thisdisclosure;

FIGS. 8A and 8B illustrate pilot patterns according to one embodiment ofthis disclosure;

FIG. 9 is a block diagram of a base station according to one embodimentof this disclosure;

FIG. 10 is a more detailed diagram of a portion of the base station ofFIG. 9 according to one embodiment of this disclosure;

FIG. 11 is a block diagram of a user element according to one embodimentof this disclosure;

FIG. 12A is a more detailed block diagram of a portion of the userelement of FIG. 11 wherein the user element is a SM enabled user elementaccording to one embodiment of this disclosure;

FIG. 12B is a more detailed block diagram of a portion of the userelement of FIG. 11 wherein the user element is a non-SM enabled userelement according to one embodiment of this disclosure;

FIGS. 13A and 13B illustrate the operation of a transparent uplink relaystation according to one embodiment of this disclosure; and

FIG. 14 is a block diagram of the transparent uplink relay station ofFIGS. 13A and 13B according to one embodiment of this disclosure.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the invention and illustratethe best mode of practicing the invention. Upon reading the followingdescription in light of the accompanying drawings, those skilled in theart will understand the concepts of the invention and will recognizeapplications of these concepts not particularly addressed herein. Itshould be understood that these concepts and applications fall withinthe scope of the disclosure and the accompanying claims.

FIG. 1 illustrates a Multimedia Broadcast Multicast Service (MBMS) zone10 of a wireless communications network according to one embodiment ofthis disclosure. The wireless communications network may be, forexample, a Fourth Generation (4G) cellular communications network suchas a Long Term Evolution (LTE) network, a WiMAX or IEEE 802.16 network,or the like. As illustrated, the MBMS zone 10 includes a number of basestations (BSs) 12-1 through 12-3 that are enabled to broadcastmultimedia content to user elements within the MBMS zone 10, such asuser elements (UEs) 14 and 16. In this embodiment, the base stations12-1 through 12-3 have multiple transmit antennas, or in other words areMultiple-Input-Multiple-Output (MIMO) devices, and transmit data using amultiple sub-carrier modulation scheme such as, but not limited to,Orthogonal Frequency Division Multiplexing (OFDM).

In general, the base stations 12-1 through 12-3 broadcast multimediacontent in such a manner as to accommodate both Spatial Multiplexing(SM) enabled user elements, such as the user element 14, and non-SMenabled user elements, such as the user element 16. More specifically,resources within a downlink channel utilized by the base stations 12-1through 12-3 are allocated for a SM mode and other resources within thedownlink channel are allocated for a non-SM mode. For OFDM, theresources allocated for the SM mode and the non-SM mode are sub-carriersduring OFDM symbol time periods. As discussed below, the resources ofthe downlink channel may be partitioned for SM mode and non-SM modeusing Time Division Multiplexing (TDM), Frequency Division Multiplexing(FDM), or a hybrid of TOM and FDM.

Using the resources allocated for the non-SM mode, the base stations12-1 through 12-3 simultaneously broadcast multimedia content for abasic service to both the SM enabled user element 14 and the non-SMenabled user element 16 using a non-SM transmit scheme. For instance,the base stations 12-1 through 12-3 may simultaneously broadcast themultimedia content for the basic service using a spatial diversitytransmit scheme. Using the base station 12-1 as an example, a spatialdiversity transmit scheme is one where the base station 12-1 transmitsthe same data stream from each of the multiple transmit antennas of thebase station 12-1 using the same time and frequency resources.

In addition, using the resources allocated for the SM mode, the basestations 12-1 through 12-3 broadcast multimedia content to the SMenabled user element 14 for an enhanced service using spatialmultiplexing. Spatial multiplexing is a transmit scheme for MIMO deviceswherein multiple transmit antennas transmit independent data streamsusing the same time and frequency resources of a transmit channel. Thus,again using the base station 12-1 as an example, when operating in SMmode, the base station 12-1 transmits independent data streams for theenhanced service from multiple transmit antennas of the base station12-1.

Thus, using the resources allocated for non-SM mode, the base stations12-1 through 12-3 simultaneously broadcast multimedia content for thebasic service to both the SM enabled user element 14 and the non-SMenabled user element 16. In other words, using the resources allocatedfor the non-SM mode, the base stations 12-1 through 12-3 broadcast thesame multimedia content for the basic service at the same time orsubstantially the same time over the same sub-carrier frequencies. Stillfurther, each of the base stations 12-1 through 12-3 using the samemodulation and coding scheme or substantially the same modulation andcoding scheme. In addition, using the resources allocated for the SMmode, the base stations 12-1 through 12-3 simultaneously broadcastmultimedia content for the enhanced service to the SM enabled userelement 14. Again, in other words, using the resources allocated for theSM mode, the base stations 12-1 through 12-3 broadcast the samemultimedia content for the enhanced service at the same time orsubstantially the same time over the same sub-carrier frequencies. Stillfurther, each of the base stations 12-1 through 12-3 using the samemodulation and coding scheme or substantially the same modulation andcoding scheme. As an example, the basic service may be a regionaltelevision station, and the enhanced service may be a local televisionstation. As another example, the basic service may be a nationaltelevision station, and the enhanced service may be one or more regionaltelevision stations and/or one or more local television stations. Notethat while television is discussed herein, the multimedia contentbroadcast by the base stations 12-1 through 12-3 is not limited thereto.Other types of exemplary multimedia content are radio content andnewspaper content including text and images.

FIGS. 2A through 2C illustrate exemplary partitions of the resources ofthe downlink channel for SM mode and non-SM mode. More specifically,FIG. 2A illustrates an example wherein the resources of the downlinkchannel used to broadcast the multimedia content are partitioned usingTDM such that all sub-carriers are allocated for SM mode during a firstperiod of time and all sub-carriers are allocated for non-SM mode duringa second period of time. The first and second periods of time may be,for example, sub-frames within a downlink frame. FIG. 2B illustrates anexample wherein the resources of the downlink channel used to broadcastthe multimedia content are partitioned using FDM such that differentblocks of sub-carriers are allocated for SM mode and non-SM mode. Forinstance, one or more blocks of sub-carriers may be allocated for SMmode during a downlink frame while one or more different blocks ofsub-carriers may be allocated for non-SM mode during the downlink frame.Lastly, FIG. 2C illustrates an example wherein the resources of thedownlink channel used to broadcast the multimedia content arepartitioned using a hybrid of TDM and FDM. For instance, differentblocks of sub-carriers may be allocated for the SM mode and the non-SMmode during each sub-frame of a downlink frame.

FIG. 3 illustrates a MBMS zone 18 that is divided into an SM zone 20 anda non-SM zone 22 according to one embodiment of this disclosure. Thisembodiment may be particularly beneficial where spatial multiplexing maybe not possible over the entire MBMS zone 18. This may occur where thecells served by base stations are relatively large such that SingleFrequency Network (SFN) improvements in Signal to Interference plusNoise Ratio (SINR) are not sufficient to provide SM in all areas withinthe cells.

In this exemplary embodiment, the MBMS zone 18 is served by basestations 24-1 through 24-8, where the base stations 24-1 through 24-5serve the SM zone 20 and the base stations 24-6 through 24-8 serve thenon-SM zone 22. The base stations 24-1 through 24-8 have multipletransmit antennas, or in other words are MIMO devices, and transmit datausing a multiple sub-carrier modulation scheme such as, but not limitedto, OFDM. Further, the base stations 24-1 through 24-5 serving the SMzone 20 simultaneously broadcast multimedia content for a basic serviceto SM enabled user elements within the SM zone 20, such as user element26, using a first layer or transmit antenna and simultaneously broadcastmultimedia content for an enhanced service using one or more additionallayers or transmit antennas using spatial multiplexing.

The base stations 24-6 through 24-8 broadcast the multimedia content forthe basic service to SM enabled user elements within the non-SM zone 22,such as user element 28, using a non-SM transmission scheme. Forinstance, in one embodiment, the base stations 24-6 through 24-8simultaneously broadcast the multimedia content for the basic serviceusing spatial diversity. The SM enabled user element 28 operates in anon-SM reception mode. For instance, the SM enabled user element 28 mayhave a decoder that is configurable in either a SM mode or a spatialdiversity (SD) mode, wherein the decoder is configured in the SM modewhen the user element 28 is in the SM zone 20 and configured in the SDmode when the user element 28 is in the non-SM zone 22. Importantly, thebase stations 24-1 through 24-8 in both the SM zone 20 and the non-SMzone 22 simultaneously broadcast the multimedia content for the basicservice using the same resources in the downlink channel. As a result,the MBMS zone 18 has advantages of a SFN, namely, improved SINR for userelements located near the cell edges as a result of over-the-aircombining of the same signals transmitted by the base stations ofneighboring cells.

In the MBMS zone 18, SM enabled user elements, such as the user elements26 and 28, are enabled to perform handoffs when moving between the SMzone 20 and the non-SM zone 22. FIG. 4 illustrates a process that may beperformed by a SM enabled user element, such as the user elements 26 and28, in order to perform a handoff between the SM zone 20 and the non-SMzone 22 as needed. More specifically, using the user element 26 as anexample, the user element 26 determines whether the user element 26 islocated with the SM zone 20 or the non-SM zone 22 (step 100). In oneembodiment, the user element 26 determines whether the user element 26is in the SM zone 20 or the non-SM zone 22 using a blind decodingtechnique. Specifically, the user element 26 may include a decoder thatis configurable as either a SM decoder or a non-SM decoder (e.g., a SDdecoder). Initially, the decoder may be configured as a SM decoder. Ifthe decoder is able to properly decode the SM broadcast signals from thebase stations 24-1 through 24-5 in the SM zone 20, then the user element26 determines that the user element 26 is in the SM zone 20, and thedecoder remains configured as a SM decoder. If the decoder is unable toproperly decode the SM broadcast signals from the base stations 24-1through 24-5 in the SM zone 20, the user element 26 determines that theuser element 26 is in the non-SM zone 22.

In an alternative embodiment, the user element 26 may determine whetherthe user element 26 is in the SM zone 20 or the non-SM zone 22 based oninformation received from one or more of the base stations 24-1 through24-8. For instance, the base stations 24-1 through 24-8 may, fromtime-to-time, transmit information identifying whether the base stations24-1 through 24-8 are in the SM zone 20 or the non-SM zone 22. Using thebase station 24-1 as an example, the base station 24-1 may transmitinformation that identifies the base station 24-1 as being within the SMzone 20. The information transmitted may be, for example, a datasequence transmitted over an access channel identifying the base station24-1 as belonging to either the SM zone 20 or the non-SM zone 22 orsignaling information transmitted over a signaling channel.

Once the user element 26 has determined whether the user element 26 isin the SM zone 20 or the non-SM zone 22, the user element 26 configuresits decoder accordingly. More specifically, if the user element 26determines that the user element 26 is in the SM zone 20, the userelement 26 enters a SM reception mode by, in this example, configuringthe decoder of the user element 26 as a SM decoder (step 102). If theuser element 26 determines that the user element 26 is not in the SMzone 20, or is in the non-SM zone 22, the user element 26 enters anon-SM reception mode by, in this example, configuring the decoder ofthe user element 26 as a non-SM decoder such as a SD decoder (step 104).

Using the process of FIG. 4, when the user element 26 moves from the SMzone 20 to the non-SM zone 22, the user element 26 determines that theuser element 26 is no longer able to decode the SM broadcast signalsfrom the base stations 24-1 through 24-5. The user element 26 thenperforms a handoff to the non-SM zone 22 by configuring the decoder ofthe user element 26 to as a non-SM decoder. In a similar manner, whenthe user element 26 moves from the non-SM zone 22 to the SM zone 20, theuser element 26 determines that the user element 26 can now properlydecode the SM broadcast signals from the base stations 24-1 through 24-5in the SM zone 20. As such, the user element 26 performs a handoff fromthe non-SM zone 22 to the SM zone 20 by configuring the decoder of theuser element 26 to operate as a SM decoder.

FIG. 5 illustrates an exemplary handoff of the user element 26 from theSM zone 20 to the non-SM zone 22 using the process of FIG. 4. Asillustrated, initially, the user element 26 is in the SM zone 20. Assuch, the user element 26 is enabled to properly decode the SM broadcastsignals from the base stations 24-1 through 24-5, and the user element26 is configured in the SM reception mode. Then, once the user element26 moves from the SM zone 20 to the non-SM zone 22, the user element 26is no longer able to properly decode the SM broadcast signals from thebroadcast stations 24-1 through 24-5. As such, the user element 26determines that the user element 26 is in the non-SM zone 22 andtherefore performs a handover from the SM zone 20 to the non-SM zone 22by entering the non-SM reception mode.

It should be noted that while the embodiments of FIGS. 1-2C and FIGS.3-5 are discussed separately, these embodiments may be used incombination. More specifically, the MBMS zone 18 may support both SMenabled and non-SM enabled user elements in the manner discussed abovewith respect to FIGS. 1-2C.

FIG. 6 illustrates two MBMS zones 30 and 32 wherein base stations 34-1through 34-9 serving the MBMS zones 30 and 32 transmit zone identifiers(IDs), or similar information, according to one embodiment of thisdisclosure. Note that while zone IDs are discussed herein, it should beappreciated that any information identifying which MBMS zone 30 or 32each of the base stations 34-1 through 34-9 is located in may be used.The base stations 34-1 through 34-5 each transmit a zone ID for the MBMSzone 30 to user elements, such as user element 36, within the MBMS zone30. Likewise, the base stations 34-5 through 34-9 each transmit a zoneID for the MBMS zone 32 to user elements, such as user element 38,within the MBMS zone 32. The zone IDs may be transmitted ascorresponding sequences within an access channel or as signalinginformation within a signaling channel. Note that the MBMS zones 30 and32 overlap and that the base station 34-5 in within both of the MBMSzones 30 and 32. As such, the base station 34-5 transmits both the zoneID for the MBMS zone 30 and the zone ID for the MBMS zone 32.

The zone IDs may be used for decoding. More specifically, the zone ID orother information identifying the base stations 34-1 through 34-5 asbelonging to the MBMS zone 30 may enable user elements within the MBMSzone 30, such as the user element 36, to identify decoding parametersneeded to decode the signals broadcast by the base stations 34-1 through34-5 for the MBMS zone 30. For example, the decoding parameters may be ascrambling code, interleaver, pilot pattern, or the like. Likewise, thezone ID or other information identifying the base stations 34-5 through34-9 as belonging to the MBMS zone 32 may enable user elements withinthe MBMS zone 32, such as the user element 38, to identify decodingparameters needed to decode the signals broadcast by the base stations34-5 through 34-9 for the MBMS zone 32. In addition or alternatively,the zone IDs may be used to indicate secondary information such as dataservice/type or the like.

FIG. 7 illustrates a handoff process for the user element 36 when movingfrom the MBMS zone 30 to the MBMS zone 32 of FIG. 6 according to oneembodiment of this disclosure. First, when the user element 36 is nearthe boundary between the MBMS zones 30 and 32, the user element 36receives zone IDs from both the base stations 34-1 through 34-5 for theMBMS zone 30 and the base stations 34-5 through 34-9 for the MBMS zone32 (steps 200-206). The user element 36 then determines whether ahandoff from the MBMS zone 30 to the MBMS zone 32 is to be performed(step 208). For example, if the strength of the signals received fromthe base stations 34-1 through 34-5 for the MBMS zone 30 is greater thanthe strength of the signals received from the base stations 34-5 through34-9 for the MBMS zone 32, then the user element 36 determines that ahandoff is not to be performed. However, if the strength of the signalsreceived from the base stations 34-5 through 34-9 for the MBMS zone 32is greater than the strength of the signals received from the basestations 34-1 through 34-5 for the MBMS zone 30, then the user element36 determines that a handoff is to be performed. Note that otherthresholds may be used in order to determine whether a handoff is to beperformed. For instance, a handoff may be performed from the MBMS zone30 to the MBMS zone 32 when the strength of the signals from the basestations 34-5 through 34-9 reach a predetermined threshold.

In this example, a handoff is to be performed. As such, the user element36 performs the handoff from the MBMS zone 30 to the MBMS zone 32 (step210). As discussed above, the zone ID may be used to identify theappropriate decoding parameters. In this case, the user element 36performs the handoff by identifying the decoding parameters for the MBMSzone 32 based on the zone ID and reconfiguring a decoder of the userelement 36 with the decoding parameters for the MBMS zone 32. Note thatwhile the discussion above focuses on zone IDs for the MBMS zones 30 and32, it should be noted that each service may be assigned a differentzone ID such that there are different MBMS zones for different services.

FIGS. 8A and 8B illustrate exemplary pilot patterns for the SM zone 20and the non-SM zone 22 of FIG. 3 according to one embodiment of thisdisclosure. As will be appreciated by one of ordinary skill in the art,pilot symbols are utilized to generate channel estimates for thedecoding process. Different pilot symbols are required for each layer,or transmit antenna. A pilot pattern defines symbol locations within atransmit frame or sub-frame at which pilot symbols are to be located.FIG. 8A illustrates a pilot symbol pattern for the SM zone 20, where inthis example the resources of the downlink channel for the SM zone 20are partitioned for SM mode and non-SM mode in order to accommodatenon-SM capable user elements in the manner discussed above with respectto FIG. 1. The pilot symbol pattern for the SM zone 20 includes pilotsymbol locations for a first layer or transmit antenna used to broadcastthe multimedia content for the basic service and additional pilot symbollocations for a second layer or second transmit antenna in the resourceblock allocated for SM mode. Common pilots are shared by the SM mode andthe non-SM mode.

FIG. 8B illustrates a pilot symbol pattern for the non-SM zone 22. Thepilot symbol pattern for the non-SM zone 22 includes the same pilotsymbol locations as the pilot symbol pattern for the SM zone 20 for theprimary layer or transmit antenna used to broadcast the multimediacontent for the basic service. This enables true SFN operation for theSM zone 20 and the non-SM zone 22.

The pilot symbol patterns discussed above are also applicable to themultiple MBMS zones 30 and 32 of FIG. 6. However, while the pilot symbollocations are preferably the same, each of the MBMS zones 30 and 32 usesa different modulation code, or sequence, to modulate the pilot symbols.Thus, the base stations 34-1 through 34-5 may use a first modulationcode to modulate the pilot symbols for the MBMS zone 30, and the basestations 34-5 through 34-9 may use a second modulation code to modulatethe pilot symbols for the MBMS zone 32. The modulation code for thepilot symbols may be determined based on the zone ID of the MBMS zone 30or 32.

If a base station belongs to more than one MBMS zone, such as the casewith the base station 34-5 of FIG. 6, then one of the followingexemplary schemes may be used for that base station. Note that a basestation belonging to more than one MBMS zone, such as the base station34-5, may provide all or some of the services from each of the differentMBMS zones with orthogonal channel resources or different layers. Usingthe base station 34-5 of FIG. 6 as an example, in one embodiment, thebase station 34-5 may broadcast MBMS data for the MBMS zones 30 and 32in different time slots such as, for example, different sub-frames. Themodulation code used to modulate the pilot symbols in a particular timeslot may then be determined based on the corresponding MBMS zone forwhich the data is being transmitted.

In another embodiment, the base station 34-5 may broadcast MBMS data forthe MBMS zones 30 and 32 using different sub-carriers. The modulationcode used to modulate the pilot symbols for a particular sub-carrier maythen be determined based on the corresponding MBMS zone for which thedata on the sub-carrier is being transmitted. In yet another embodiment,the base station 34-5 may broadcast MBMS data for the MBMS zones 30 and32 using different MIMO layers. The modulation code used to modulate thepilot symbols for a particular MIMO layer may then be determined basedon the corresponding MBMS zone.

FIG. 9 is a block diagram of a base station 40. This discussion of thebase station 40 is applicable to the base stations 12-1 through 12-3,24-1 through 24-9, and 34-1 through 34-9 discussed herein. Asillustrated, the base station 40 generally includes a control system 42,a baseband processor 44, OFDM transmit circuitry 46, receive circuitry48 which in this example is Single-Carrier Frequency Division MultipleAccess (SC-FDMA) receive circuitry, multiple antennas 50, and a networkinterface 52. FIG. 10 illustrates the baseband processor 44 and the OFDMtransmit circuitry 46 of FIG. 9 in more detail. As illustrated, acoding/modulation primitive 54 is responsible for encoding,interleaving, and modulating binary data to generate data symbols, as iswell known to those skilled in the art. The coding/modulation primitive54 may include a number of processing blocks, not shown in FIG. 10. Anencoder 56 applies either spatial multiplexing encoding or spatialdiversity encoding to the data symbols depending on the mode ofoperation. The encoder 56 also separates the data symbols into differentprocessing paths to corresponding OFDM components 58. Each OFDMcomponent 58 receives data symbols from the encoder 56, processes thedata symbols according to a desired OFDM modulation scheme, andtransmits the modulated data symbols via the corresponding antenna 50.

FIG. 11 is a block diagram of a user element 60. This discussion of theuser element 60 is applicable to the user elements 14, 16, 26, 28, 36,and 38 discussed herein. As illustrated, the user element 60 generallyincludes a control system 62, a baseband processor 64, transmitcircuitry 66 which in this example is SC-FDMA transmit circuitry, OFDMreceive circuitry 68, multiple antennas 70, and a user interface 72.FIG. 12A illustrates the baseband processor 64 and the OFDM receivecircuitry 68 of FIG. 11 for an embodiment wherein the user element 60 isSM enabled. As illustrated, the user element 60 includes multiple OFDMcomponents 74, each connected to one of the antennas 70. Each OFDMcomponent 74 processes received signals according to the desired OFDMmodulation scheme, as will be appreciated by one of ordinary skill inthe art. The OFDM components 74 output data symbols to a decoder 76. Thedecoder 76 applies either spatial multiplexing decoding or spatialdiversity decoding and passes the symbols to a decoding/demodulatingprimitive 78 responsible for decoding, de-interleaving, and demodulatingthe symbols to generate output binary data, as is well known to thoseskilled in the art. The decoding/demodulation primitive 78 may include anumber of additional processing blocks, which are not shown in FIG. 12A.FIG. 12B is similar to FIG. 12A. However, FIG. 12B illustrates thebaseband processor 64 and the OFDM receive circuitry 68 of FIG. 11 foran embodiment wherein the user element 60 is not SM enabled. In thisembodiment, there is only one OFDM component 74.

FIGS. 13A and 13B illustrate the operation of a transparent uplink relaystation (RS) 80 according to another embodiment of this disclosure. Notethe transparent uplink RS 80 may be utilized in any type of cellularcommunications network and is not to be construed as being limited to acellular communications network providing MBMS based on the discussionabove. The transparent uplink RS 80 may be utilized in any type ofwireless communications network such as an LTE cellular communicationsnetwork, a WiMAX or IEEE 802.16 network, or the like. More specifically,as illustrated in FIG. 13A, a user element 82 first transmits uplinkdata to a base station 84 according to an uplink grant (step 300). Boththe transparent uplink RS 80 and the base station 84 decode the uplinkdata (steps 302 and 304). Note that prior to step 300, the transparentuplink RS 80 preferably decodes uplink grant information transmitted bythe base station 84 for the user element 82. In this embodiment, thebase station 84 decodes the uplink data correctly. As such, the basestation 84 sends an acknowledgement (ACK) message to the user element 82(step 306). Both the user element 82 and the transparent uplink RS 80detect the ACK message (steps 308 and 310). As such, no relay is need.Therefore, the transparent uplink RS 80 discards the uplink data (step312).

FIG. 13B illustrates the operation of the transparent uplink RS 80 wherethe uplink data is not correctly decoded by the base station 84. Asillustrated, the user element 82 first transmits uplink data to the basestation 84 according to an uplink grant (step 400). Both the transparentuplink RS 80 and the base station 84 decode the uplink data (steps 402and 404). In this embodiment, the base station 84 does not decode theuplink data correctly. As such, the base station 84 sends an NAK messageto the user element 82 (step 406). Both the user element 82 and thetransparent uplink RS 80 detect the NAK message (steps 408 and 410). Assuch, assuming the transparent uplink RS 80 decoded the uplink datacorrectly, the user element 82 retransmits the uplink data (step 412),and the transparent uplink RS 80 also retransmits the uplink datasimultaneously with the retransmission of the uplink data from the userelement 82 (step 414). Preferably, the transparent uplink RS 80retransmits the uplink data using the same physical, or radio, resources(e.g., time and frequency) as well as the same modulation and codingscheme as the user element 82 such that the retransmission of the uplinkdata from the user element 82 and the transparent uplink RS 80 combineover the air (i.e., at the receive antenna(s) of the base station 84),thereby improving the SINR of the corresponding signal received by thebase station 84. The base station 84 decodes the uplink data (step 416).Assuming the base station 84 decoded the uplink data correctly, the basestation 84 sends an ACK message to the user element 82 (step 418). Inthis embodiment, both the user element 82 and the transparent uplink RS80 detect the ACK (steps 420 and 422). The transparent uplink RS 80 thendiscards the uplink data (step 424).

The user element 82 and the base station 84 are implemented in hardware.For example, the user element 82 may be implemented similar to the userelement 60 of FIG. 11, and the base station 84 may be implementedsimilar to the base station 40 of FIG. 9. FIG. 14 is a block diagram ofthe transparent uplink RS 80 according to one embodiment of thisdisclosure. As illustrated, the transparent uplink RS 80 includes acontrol system 86, which may have associated memory 88. The controlsystem 86 is implemented in hardware. For instance, the control system86 may be implemented as one or more central processing units (CPUs),one or more Application Specific Integrated Circuits (ASICs), one ormore Field Programmable Gate Arrays (FPGAs), or the like, or anycombination thereof. The functions of the transparent uplink RS 80 maybe implemented in software and stored in the memory 88, implemented ashardware functions within the control system 86, or a combinationthereof. The transparent uplink RS 80 also includes one or more wirelesscommunication interfaces 90 for sending messages to and/or receivingmessages from the user element 82 and the base station 84 as needed.

Preferably, the transparent uplink RS 80 is independent of wirelesscommunications standards and transparent to the user element 82. Thebase station 84 may have knowledge of the transparent uplink RS 80 andtreat the transparent uplink RS 80 the same as the user element 82. Ascheduler of the base station 84 may be enabled to sense the existenceof the transparent uplink RS 80 using, for example, channel statisticsand employ a relay trigging scheduling approach to fully take advantageof the transparent uplink RS 80. The transparent uplink RS 80 makessynchronous Hybrid Automatic Repeat Request (H-ARQ) easy to implement,as there is no coordination needed between the transparent uplink RS 80and the user element 82. Also, preferably, the transparent uplink RS 80does not have any signaling of its own and does not take any additionalradio resources.

Those skilled in the art will recognize improvements and modificationsto the embodiments of the present invention. All such improvements andmodifications are considered within the scope of the concepts disclosedherein and the claims that follow.

What is claimed is:
 1. A wireless communications network providingMultimedia Broadcast Multicast Service (MBMS) comprising: one or morefirst base stations serving a first MBMS zone and configured to transmitinformation identifying the one or more first base stations as belongingto the first MBMS zone; and one or more second base stations serving asecond MBMS zone and configured to transmit information identifying theone or more second base stations as belonging to the second MBMS zone;wherein a plurality of user elements located in the first and secondMBMS zones are enabled to transition between the first and second MBMSzones based on the information transmitted by the one or more first basestations identifying the one or more first base stations as belonging tothe first MBMS zone and the information transmitted by the one or moresecond base stations identifying the one or more second base stations asbelonging to the second MBMS zone, wherein the information comprises arespective MBMS zone ID which is used for decoding data in thecorresponding zone, including in determining a scrambling code and asequence for modulation of pilots of the respective MBMS zone.
 2. Thewireless communications network of claim 1, wherein the informationtransmitted by the one or more first base stations and the informationtransmitted by the one or more second base stations comprise respectivesequences transmitted over an access channel.
 3. The wirelesscommunications network of claim 1, wherein transitioning between thefirst and second MBMS zones based on the information transmitted by theone or more first base stations identifying the one or more first basestations as belonging to the first MBMS zone and the informationtransmitted by the one or more second base stations identifying the oneor more second base stations as belonging to the second MBMS zonecomprises comparing signal strengths of signals transmitted by at leastone of the one or more first base stations and signal strengths ofsignals transmitted by at least one of the one or more second basestations.
 4. The wireless communications network of claim 1, wherein thepilots of each MBMS zone are scattered throughout the time and frequencyresources of that MBMS zone according to a pilot pattern.
 5. Thewireless communications network of claim 1, wherein the one or morefirst base stations and the one or more second base stations comprises aplurality of antennas, wherein for each antenna configured for the firstMBMS zone or the second MBMS zone, the pilot pattern is the same for therespective MBMS zone.
 6. The wireless communications network of claim 1,wherein data of the first and second MBMS zones are transmitted in adifferent time slot and/or frequency band.
 7. The wirelesscommunications network of claim 1, wherein first and second pilotsymbols of the first MBMS zone and the second MBMS zone of aretransmitted on a different frequency band.
 8. The wirelesscommunications network of claim 1, wherein the information transmittedby the one or more first base stations and the information transmittedby the one or more second base stations are transmitted by each of thebase stations periodically through a signaling channel.
 9. The wirelesscommunications network of claim 1, wherein a first base station iscomprised in both the first one or more base stations and the second oneor more base stations.
 10. A base station providing Multimedia BroadcastMulticast Service (MBMS) comprising: a wireless interface; at least oneprocessing element coupled to the wireless interface, the processingelement configured to: serve a first MBMS zone and transmit firstinformation identifying the base station as belonging to a first MBMSzone; and serve a second MBMS zone and transmit second informationidentifying the base station as belonging to a second MBMS zone; whereina plurality of user elements located in the first and second MBMS zonesare enabled to transition between the first and second MBMS zones basedon the first information transmitted by the base station identifying thebase station as belonging to the first MBMS zone and the secondinformation transmitted by the base station identifying the base stationas belonging to the second MBMS zone, wherein each of the firstinformation and the second information comprises a respective MBMS zoneID which is used for decoding data in the corresponding zone, includingin determining a scrambling code, and a sequence for modulation ofpilots of the respective MBMS zone.
 11. The base station of claim 10,wherein the pilots of each MBMS zone are scattered throughout the timeand frequency resources of that MBMS zone according to a pilot pattern.12. The base station of claim 10, wherein the base station comprises aplurality of antennas, wherein for each antenna configured for the firstMBMS zone or the second MBMS zone, the pilot pattern is the same for therespective MBMS zone.
 13. The base station of claim 10, wherein data ofthe first and second MBMS zones are transmitted in a different time slotand/or frequency band.
 14. The base station of claim 10, wherein firstand second pilot symbols of the first MBMS zone and the second MBMS zoneof are transmitted on a different frequency band.
 15. The base stationof claim 10, wherein the first information and the second informationare transmitted by each of the base station periodically through asignaling channel.
 16. A method for providing Multimedia BroadcastMulticast Service (MBMS) comprising: by a base station: serving a firstMBMS zone and transmitting first information identifying the basestation as belonging to a first MBMS zone; and serving a second MBMSzone and transmitting second information identifying the base station asbelonging to a second MBMS zone; wherein a plurality of user elementslocated in the first and second MBMS zones are enabled to transitionbetween the first and second MBMS zones based on the first informationtransmitted by the base station identifying the base station asbelonging to the first MBMS zone and the second information transmittedby the base station identifying the base station as belonging to thesecond MBMS zone, wherein each of the first information and the secondinformation comprises a respective MBMS zone ID which is used fordecoding data in the corresponding zone, including in determining ascrambling code, and a sequence for modulation of pilots of therespective MBMS zone.
 17. The method of claim 16, wherein the pilots ofeach MBMS zone are scattered throughout the time and frequency resourcesof that MBMS zone according to a pilot pattern.
 18. The method of claim16, wherein the base station comprises a plurality of antennas, whereinfor each antenna configured for the first MBMS zone or the second MBMSzone, the pilot pattern is the same for the respective MBMS zone. 19.The method of claim 16, wherein data of the first and second MBMS zonesare transmitted in a different time slot and/or frequency band.
 20. Themethod of claim 16, wherein first and second pilot symbols of the firstMBMS zone and the second MBMS zone of are transmitted on a differentfrequency band.